In January, the index equaled 124.4 versus 130 in December. The all-time high of 131 was in November 2013. Compared to January 2013, the latest reading is still 1.2% higher. ATA calculates the tonnage index based on surveys from its membership.

ATA recently revised the index back five years as part of its annual revision. For all of 2013, tonnage was up 6.3%, slightly better than the 6.2% originally reported. In 2012, the index increased 2.3%.

“Like most economic indicators, truck tonnage was negatively impacted by bad winter weather in January,” said ATA chief economist Bob Costello. “The thing about truck freight is that it’s difficult to catch up. Drivers are governed by hours-of-service regulations and trucks are limited to trailer lengths and total weights, thus it is nearly impossible to recoup the days lost due to bad storms.”

As a result, Costello said January will be a tough month to gauge.

“January wasn’t just one storm, it was several across a large part of the country. Therefore, I wouldn’t panic from the largest monthly drop in two years," Costello said. "I’ve heard from many fleets that freight was good, in-between storms. The fundamentals for truck freight still look good.”